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Everytime I reboot my HP dm4 Pavillion the brightness is zero on my screen. BTW I use a Ubuntu 12.04..

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Is that the darkest, lowest setting? – belacqua Nov 13 '12 at 17:16

You can try this:-

edit the file /etc/rc.local

before the last line 'exit 0' add the following line:

echo 4 > /sys/class/backlight/acpi_video0/brightness

save and reboot.

This should then set your brightness. I will add the caveat that this doesn't always work with HP machines but hopefully you'll be OK.

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